Specific gravity measuring device



April 7, 1942..

J. F. LUHRS SPECIFIC GRAVITY MEASUREMENT DEYI CE Original Filed Nov; 16, 1958 Patented Apr. 7, 1942 I uiran STATES PATENT OFFICE srscmc GRAVITY MEASURING navrcs John F. Luhrs, Cleveland Heights, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Original application November 16, 1938, Serial No. 240,599Vg.

Divided and this application This application is a division of Irwin and Luhrs application Serial No. 24059926, flled November 16, 1938.

The present invention relatesgenerally to an apparatus for determining the properties of a fluid, and more particularly to anapparatus for continuously determining the in situ speciflc gravity of a flowing fluid undergoing a change or conversion.

In the processing of flowing fluids, it is frequently desirable for control purposes to have a continuous record or indication of the in situ specific gravity of the fluid, without withdrawing' a sample and determining its properties bymeans of a hydrometer, Westphal balance, or other laboratory methods applicable to withdrawn samples. The periodic determination of specific gravity of a withdrawn sample is a difficult and expensive operation in any case, and of little or no value as far as indicating the corre= sponding property of the fluid in its flowing condition, especially when dealing with fluids at temperatures and pressures which are materially different from-atmospheric conditions. In addition, such cold sampling procedures are not applicable for the determination of the in situ properties of fluid mixtures which are not stable at atmospheric conditions. Thus, the mixture may be rapidly undergoing a change or conversion with the result that the character of the analyzed sample would materially differ from that of the sample at the instant of its withdrawal, Likewise, the fluid in its flowing state might comprise a mixture of gas, vapor and liquid, in which case the analysis of a withdrawn sample would fail to indicate the specific gravity of the fluid under the conditions obtaining in theflowing stream. For these and other reasons, it is highly desirable to employ a technique and apparatus which is capable of reflecting the in situ specific gravity of the flowing fluid stream, and thereby aflord a continuous indication or record of the fluid properties under actual flowing conditions.

One of the objects of the presentinvention to provide anapparatus for determining the in situ specific gravity of a fluid under flowing conditions.

Another object is to provide an apparatus for determining the in situ properties of a fluid undergoing a change or conversion while flowing in the form of a stream.

Another object is an apparatus for determining the in situ specific gravity of a flowing fluid,'.

which is applicable not.only to liquids or gases or vapors, but also to mixtures thereof.

The foregoing objects may be accomplished in accordance with the present invention, one aspect of which includes an apparatus which continuously compares the weight per unit area of a vertical column of a fluid, the speciflcgravity' vor reference fluid being maintained at the same temperature as the fluid whose specific gravity is being determined.

In order more clearly to disclose the nature of the present invention, reference is made to the accompanying drawing wherein several illustrative forms of the apparatus contemplated by the present invention are diagrammatically shown. It should be understood, however, that the present invention is by no means restricted to the embodiment, hereinafter more particu-- larly described, the drawing being merely illustrative of the principles involved.

Referring generally to the drawing,

Figure 1 is a sectional elevation of a simple form of apparatus in accordance with the present invention, the conduit for the reference fluid being centraly disposed within the conduit for the main fluid stream, in this embodiment.

Fig. 2 is a fragmentary cross-sectional view along the line 2-2 of Fig. l. v

Fig. 3 is a cross sectional view of a modified form of sealing pot which may be used where the reference fluid is miscible with the fluid whose specific gravity is to be determined.

Fig. 4 is a view partly in section and partly in elevation of a modified form of the invention wherein the connecting line-is spirally wound around the main fluid conduit.

Fig. 5 is a view partly in section and partly in elevation of a modified form of the invention which may be used when the velocity of flow through the main conduit is-high.

Fig. 6 is an enlarged sectional elevation showapproximately constant by any suitable means (not shown), well known inthe art. and at a 1 section of the conduit indicated by the letter B.

Centrally disposed in the main vertical conduit I I is a smaller conduit ll, thetop of which is provided with an enlarged cup ii, to provide a sealing means. The lower end of conduit ll passes through a sealed opening in the wall of the larger conduit Ill, and connects through line II with oneleg of a U-tube or manometer l4 containing a sealing liquidC, such as mercury, for example. The opposite leg of the U-tube I4 is connected by conduit I! to tap-oi! connection I, sealing means l'l. being interposed between conduits l5 and ii. A valve i8 is placed in line I. if desired. Conduits II, It, IS, and ll,'-and the upper portion of each leg of the U-tube I, are filled with a reference or standard fluid B which is preferably immiscible with the fluid A, under the conditions prevailing in column II. A'static head of fluid B is exerted on both sides of the U-tube or manometer l4, above the seal-1 ing fluid C. The position of the indicator arm 20 positioned by a float in one leg of the U-tube with reference to chart or scale 2| is determined by the relative position of the sealing liquid C. Since the reference fluid B is maintained at the same temperature as the fluid A, the scale or chart 2| may be calibrated to read specific gravity.

' Fig. 3 shows a sealing pot which may be used in lieu of that shown in Fig. l, where the reference fluid B is miscible with the fluid A whose specific gravity is to be determined. The sealing pot includes an expansible'thin-wall bellows lib, which is sealed in the opening in the top of the As shown inFig. 7, this nipple may be adjusted so that the increase in velocity head may be made to correspond exactly to the increase in pressure drop. With the nipple 3| pointing downstream, full velocity head will of course be attained. If, however, the nipple is rotated, the per cent of velocity head would be decreased so that at 90 there would be substantially no velocity head impressed on the other connection. By flowing a fluid of constant density through the pipe, but at difierent velocities, the nipple may be adjusted so that, regardless of such change in velocity, the recording or indicating arm 20 remains at the correct reading. In this manner variations caused by friction loss may be overcome.

By specific gravity I mean the relative density of a substance as compared with some standard substance, 1. e. the ratio of the mass of a certain volume to the mass of an equal volume of a standard at some reference temperature.

To obtain accurate specific gravity measurements, the reference fluid B should have the same 'coeflicient of expansion as the flowing fluid A while fluid B flows in and out of conduit II.

Fig. 4 shows an alternative scheme for maintaining the conduit II at the same temperature as the flowing fluid A. According to this embodiment the connecting line H is spirally wrapped around the outer wall of conduit ID, a lagging 23 being placed around the'tap-ofl connection 24, the sealing pot l2, and the spirally disposed line H, to maintain the temperature of the fluid in the connecting line H substantially at the temperature of the fluid within the conduit N.

Fig. 5 shows an embodiment adapted for use when the velocity of the fluid flowing through the vertical'conduit" I O:is relatively high, a portion of the fluid being by-passed through conduit Ila by maintaining a pressure drop across an adjustable valve 28. the flow through the by-pass being regulated by valve 21. The upper connectingconduit'll connects to by-pass lfla and is disposed within the main conduit It, in order to maintain the reference fluid at the temperature of the main stream. The other tap-off connection is likewise taken oi! from the by -pass lid.

The remainder of the parts are similar to those shown in Fig. l.

. In Figs. sand 7 is shown a modified form of nipple which may be used at the upper connection in Fig. 4, for example, to compensate for pressure drop due to friction loss if the rate of flow of the fluid through column II is too great.

In general, the pressure drop can be minimized mayalso be employed to this end, either with or without the use of a large diameter conduit. As

shown in Fig. 6, the head ll 01 the nipple is bent For this purpose a mixture of glycerin and water, for example, may be used, inasmuch as by varying the percentages of each of these constituents it is possible to obtain a mixture having the same coefilcientof expansion a practically any-known fluid. Accordingly, by employing a liquid 13 in the connecting lines having the same coefflcient of expansion as fluid A, and maintaining the connecting lines at'the same temperature as that of fluid A, the apparatus will provide sensitive means for indicating or recording variations in the specific gravity of the fluid in the conduit wherein changes are likely to occur.

In the foregoing detailed description it is apparent that many variations may be made without' departing from the spirit and scope of the invention. I therefore intend to be restricted I only in accordance with the following claims.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. Apparatus for continuously determining the specific gravity of a given portion of a vertically flowing liquid stream confined in a conduit comprising means forming a column of reference liquid having the same coefficient ofexpansion as the liquid stream, means external to the flowing stream adapted to continuously compare the weight per unit area of the portion of the vertical column of the liquid stream with the weight per unit area of an equal length vertical column of the reference liquid having the same coeflicient of expansion as the liquid stream, said means including a U-tube, one leg' of which is connected to the said liquid stream in said conduit and the other leg thereof is connected to the bottom of the column of reference liquid, and

means tending ,to keep the temperature of the two columns being compared uniform.

2. Apparatus forcontinuously determining the specific gravity of a flowing confined liquid stream comprising, mean; forming a stationary column having substantially the same specific gravity as the flowing stream, the two said columns being maintained at the same temperature, and means compensating for variations in velocity of the flowing stream, said means comprising a by-pass line joining spaced points of said fluid stream and communicating with the top of said vertical column.

JOHN F. LUHRS. 

